Seasonal diets of the gemsbok (Oryx gazella gazella) at Mason Mountain Wildlife Management Area, Mason County, Texas




Winters, Amy

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I investigated the seasonal diets of gemsbok antelope (Oryx gazella gazella) at Mason Mountain Wildlife Management Area using microhistological analysis of fecal pellets. Plants in 2,000 samples were identified to genus or species. Vegetational surveys were conducted using the Daubenmire and line intercept methods. In order to determine selectivity, dietary use was compared to availability of food plants using the Manly's alpha measure of dietary preference index and a log-likelihood chi-square statistic with Bonferroni correction. Results indicated that gemsbok were predominately grazers with grasses comprising 74.35% of the diet. Browse made up 25% and forbs 0.65% of the annual diet. A total of 40 plant species were consumed by gemsbok during the year. I found that gemsbok grazed selectively. However, plant species that made up large proportions of the diet were not necessarily selected. The plants used in greatest quantity were little bluestem (Schizachyrium scoparium) (12.5%), side oats grama (Bouteloua curtipendula) (9.75%), twistedleaf yucca (Yucca rupicola) (9.9%), and the category "other" (16.45%), which contained all species with less than 2% occurrence in the diet. Annually, selected plants were Canada wildrye (Elymus canadensis), Chloris sp., honey mesquite (Prosopis glandulosa), and twistedleaf yucca. Seasonally, the most selected plants were Chloris sp. and twistedleaf yucca in summer. Sideoats grama and vine-mesquite (Panicum obtusum) were selected in winter and spring'. Plains lovegrass (Eragrostis intermedia) was selected in fall and winter. Canada wildrye was highly selected in fall. These results indicate a potential for competition between gemsbok and domestic livestock. In managing ranches with gemsbok present, the species should be considered when determining stocking rates and grazing regimes for domestic livestock.



seasonal diets, animals, wildlife management, Mason County, gemsbok


Winters, A. (2002). Seasonal diets of the gemsbok (Oryx gazella gazella) at Mason Mountain Wildlife Management Area, Mason County, Texas (Unpublished thesis). Southwest Texas State University, San Marcos, Texas.


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